Conveyor chain

ABSTRACT

A reduced friction conveyer chain is used for conveying aluminum cans, glass bottles, PET bottles and other objects in a conveyer chain system where such objects are produced continuously. The conveyer chain is especially useful in the system where the objects being conveyed are slid on the surface of the chain and relatively thereto. Since the kinetic friction coefficient of the outer surfaces of the links, which constitute the conveyer chain and on which the objects to be conveyed are put, is reduced, the slidability of the links is improved, and the bottom surfaces of the objects being conveyed are prevented from being scratched.

TECHNICAL FIELD

The present invention relates to a conveyer chain and, more precisely,to a conveyer chain capable of promoting the slidability of its outersurface on which objects are conveyed while reducing the damage of thebottom surfaces of the objects being slid.

BACKGROUND ART

In the conveyer system of continuously producing aluminium cans, glassbottles, PET bottles and others, conveyer chains are much used as themeans of conveyance of such objects. This system of using conveyerchains includes the steps of stopping the stream of the objects beingconveyed and drawing up them in order in the middle of the conveyancethereof, in which the objects must be slid on the conveyer chainrelatively thereto in such steps of stopping the stream of the objectsand drawing up them in order.

One example of promoting the slidability of the outer surface of such aconveyer chain is to employ chains made of resins. Heretofore,polyoxymethylene resins, polyetherimide resins or fluorine-containingresins have been used as the materials of the links for resin chains ofconveyers. However, such plastic links are greatly worn away, as havingpoor hardness, and their life is therefore short. If graphite is addedto such plastic links in order to enhance their hardness, their kineticfriction coefficient is lowered. However, the graphite added drops outdue to friction to produce dust, which is problematic in that the dustis incorporated into the inside and the surface coats of the objectsbeing conveyed to thereby worsen the quality of the objects and that thedust has some negative influences on the electronic circuits in theadjacent devices.

In practical conveyer system lines, a lubricant such as water or soapywater is applied onto the outer surfaces of conveyer chains to therebypromote their slidability. In general, however, since the outer surfacesof conventional conveyer chains on which objects are conveyed are flat(see Japanese Utility Model Application Laid-Open No. 57-49812), objectsare conveyed thereon with their bottom surfaces being tightly attachedon the outer surfaces of the conveyer chains. Accordingly, even if sucha lubricant is applied onto the outer surfaces of the conveyer chains inorder to promote their slidability, the lubricant is stripped off fromthe outer surfaces of the conveyer chains by the bottom surfaces of theobjects being conveyed thereon, resulting in that the slidability of theouter surfaces of the conveyer chains is still insufficient.

If relatively hard, fine impurities, such as glass powder or metalpowder, adhere to the outer surfaces of conveyer chains, such causesanother problem in that the bottom surfaces of objects being conveyed onthe conveyer chains are scratched by the fine impurities.

Therefore, the object of the present invention is to provide a conveyerchain capable of promoting the slidability of its outer surface on whichobjects are conveyed while reducing the damage of the bottom surfaces ofthe objects being slid.

SUMMARY OF THE INVENTION

The present invention provides a conveyer chain comprising a pluralityof links linked endlessly to one another in such a manner that the frontend of one link is movably linked to the back end of the adjacent linkvia a linking pin, which is characterized in that the outer surfaces ofthe links on which objects to be conveyed are located have a kineticfriction coefficient of less than 0.3 as measured in the test where analuminium object is slid against the outer surfaces of the links at apressure of 5 kg/cm² and at a peripheral velocity of the chain of 20m/min.

In this condition, the slidability of the outer surface of the conveyerchain of the invention relative to the objects being conveyed thereon ispromoted while the damage to the bottom surfaces of the objects beingslid is reduced, when the conveyance of the objects is stopped and/orthe objects are drawn up in order in the middle of the conveyance line.

As one embodiment of the conveyer chain of the invention, the outersurfaces of the links on which objects to be conveyed are put are formedto have thereon a plurality of small hills and grooves.

The plurality of small hills and grooves as formed on the outer surfacesof the links reduce the area of the outer surfaces to be kept in contactwith the bottom surfaces of the objects being conveyed, thereby reducingthe frictional resistance between them and improving the slidability ofthe outer surfaces of the links relative to the objects being conveyed.In addition, even if fine impurities with high hardness, such as glasspowder and metal powder adhere on the outer surface of the conveyerchain of the invention, they are pushed by the bottom surfaces of theobjects being conveyed into the grooves formed on the links whereby thebottom surfaces of the objects are prevented from being scratched bythem.

Preferably, a lubricant is applied onto the outer surface of theconveyer chain of the invention on which objects to be conveyed arelocated. The lubricant is kept in the grooves formed on the links and isgradually released little by little toward the outer surface of theconveyer chain, by which the slidability of the outer surface of theconveyer chain is much more promoted. In addition, since the lubricantis so kept in the grooves and gradually released toward the outersurface, any continuous application of a large amount of lubricant as inconventional conveyer chains is unnecessary and only a small amount oflubricant may well be applied to the conveyer chain of the invention.

As another embodiment, the links of the conveyer chain of the presentinvention are made from a composition comprising a polyamidimide resinand a fluorine-containing resin.

The kinetic friction coefficient of the outer surface of the conveyerchain composed of such resin links is much reduced and, in addition, itscritical PV value can be optimized. Moreover, since the resin links havehigh creeping resistance, the conveyer chain composed of these isneither elongated nor loosened. Therefore, it is unnecessary toartificially control the conveyer chain to prevent it from beingloosened, and the labor for maintaining the conveyer chain can be saved.

Further, the present invention also provides the use of the conveyerchain mentioned above, which is characterized in that the objects beingconveyed on the conveyer chain are slid on at least a part of the outersurface of the conveyer chain, relative to the outer surface of theconveyer chain being contacted with the objects.

In this use, the conveyer chain of the invention can specificallyexhibit its characteristics while preventing the bottom surfaces of theobjects being conveyed and slid thereon from being scratched.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view partly showing one embodiment of theconveyer chain of the present invention, which has a plurality of smallhills and grooves on its outer surface on which objects to be conveyedare put.

FIG. 2 is a cross-sectional view as taken along the A--A line of FIG. 1.

FIG. 3 is a partial plan view of a conveyor chain of the invention.

FIG. 4 is a partial cross-sectional view taken along line 4--4 of FIG.3.

FIG. 5 is a partial cross-sectional view taken along line 5--5 of FIG.3.

BEST MODES OF CARRYING OUT THE INVENTION

The conveyer chain of the present invention comprises a plurality oflinks linked endlessly to one another in such a manner that the frontend of one link is movably linked to the back end of the adjacent linkvia a linking pin, which is characterized in that the outer surfaces ofthe links on which objects to be conveyed are located have a kineticfriction coefficient of less than 0.3 as measured in the test where analuminium object is slid against the outer surfaces of the links at apressure of 5 kg/cm² and at a peripheral velocity of 20 m/min.Preferably, the kinetic friction coefficient is 0.29 or less, morepreferably 0.20 or less.

The kinetic friction coefficient is of the outer surface of the conveyerchain on which objects to be conveyed are located, and is measuredaccording to the method mentioned below.

Using a Suzuki-type abrasion tester, an aluminium object is slid againstthe outer surface of the conveyer chain on which objects to be conveyedare located, at a pressure of 5 kg/cm² and at a peripheral velocity of20 m/min for a period of 1 hour, whereupon the kinetic friction factorof the outer surface of the conveyer chain is measured.

In the present invention, the shape of the conveyer chain and thematerial of the outer surface thereof on which objects to be conveyedare put must be selected in order that the kinetic friction coefficientof the outer surface of the conveyer chain can fall within theabove-defined range. Though not specifically limited for this purpose,preferred are, for example, a chain composed of links each having aplurality of small hills and grooves as formed on their outer surfaceson which objects to be conveyed are located; the chain composed of suchlinks, to which is applied a lubricant on its outer surface having suchsmall hills and grooves; a chain composed of links, at least the outersurfaces of which to be contacted with the objects being conveyed aremade from a composition comprising a polyamidimide resin and afluorine-containing resin; and a chain composed of such links, at leastthe outer surfaces of which to be contacted with the objects beingconveyed are made from a composition comprising a polyamidimide resinand a fluorine-containing resin, and which have a plurality of smallhills and grooves as formed on their outer surfaces that are contactedwith the objects being conveyed.

These chains are described in detail hereinunder.

First, the chain composed of links each having a plurality of smallhills and grooves as formed on their outer surfaces on which objects tobe conveyed are located is described in detail. In order to make itpossible to more easily understand the chain of this type, the drawingsattached hereto are referred to.

FIG. 1 is a perspective view partly showing one embodiment of theconveyer chain of the present invention, which has a plurality of smallhills and grooves on its outer surface on which objects to be conveyedare located. In this, 1 is a link, on the outer surface of which are putobjects to be conveyed. A plurality of these links 1 are endlesslylinked to one another in line to constitute the conveyer chain 10 thatmoves in the direction of the arrow, F.

Each link 1 has a joint 1a at its front end in the center thereof in thewidthwise direction and has a forked joint 1b, 1b at the both sides ofthe back end. The joint 1a is linked to the forked joint 1b, 1b of theadjacent link 1 between 1b and 1b. These joints 1a and 1b are providedwith pin holes 2a and 2b, respectively, that pass therethrough in thewidthwise direction, and a metal pin (not shown) is inserted into theholes, via which the adjacent links are relatively movable.Needless-to-say, in these links 1, the forked joint 1b, 1b may be at thefront end of each link while the central joint 1a may be at the back endthereof. Each link 1 has on the entire outer surface thereof, on whichobjects to be conveyed are located, a plurality of long, small hills 3and a plurality of long grooves 4 as formed alternately in parallel toone another and extending in the moving direction (that is, in thedirection of the arrow, F). It is desirable that these hills and groovesare formed on the entire outer surface of each link on which objects tobe conveyed are located, but it is not always necessary to form these onthe entire outer surface. Depending on the kind of the objects to beconveyed on the conveyer chain, the small hills and the grooves may bepartly formed on the outer surface of each link.

As in FIG. 2, the profile of the cross section of each small hill 3 istrapezoidal, while that of the cross section of each groove 4 isinverted-trapezoidal, and therefore the side walls of the small hillsare inclined. Precisely, the profile of the cross section of each smallhill 3 is tapered toward the outer surface of the link, while that ofthe cross section of each groove 4 is broadened toward it. With suchprofiles of the small hills and grooves, the outer surface of the linkis waved in the widthwise direction thereof.

The shapes of these hills and grooves are not specifically defined,provided that the hills and grooves can constitute a structure capableof reducing the contact area between the outer surface of the link andthe objects to be located thereon. Preferably, however, a plurality oflong, small hills and a plurality of grooves are alternately formed onthe outer surface of each link in its lengthwise direction. Morepreferably, these small hills and grooves are formed alternately whileextending in parallel to one another in the moving direction of theconveyer chain. With such a structure, the conveyer chain can carry theobjects being conveyed thereon. Apart from this, each link may have aplurality of long grooves that extend in the moving direction of thelink and a plurality of long grooves that extend in the transversedirection relative to the moving direction, along with a number ofindependent small hills as surrounded by these grooves. Such a number ofindependent small hills in this case may be laid out at right angleslike a checkerboard, or may be laid out in a zigzag pattern, or may evenbe laid out at random. In any case, it is desirable that the profile ofthe cross section of each of such long, small hills and independentsmall hills is substantially trapezoidal, while that of the crosssection of each groove is substantially inverted-trapezoidal. It is alsodesirable that the height of each hill is substantially on the samelevel.

Regarding the relationship between the long, small hills 3 and theadjacent grooves 4, it is desirable that the pitch, P of the hills 3sandwiched between the adjacent grooves 4 is from 0.5 to 2.0 mm,preferably from 0.8 to 1.5 mm, while the depth, D of each groove 4 isfrom 0.2 to 2.0 mm, preferably from 0.5 to 1.5 mm. The same shall applyalso to the relationship between the independent hills and the groovesthat surround the hills. That is, the pitch of the hills is desirablyfrom 0.5 to 2.0 mm, more desirably from 0.8 to 1.5 mm, while the depthof each groove is desirably from 0.2 to 2.0 mm, more desirably from 0.5to 1.5 mm.

With such small hills 3 and grooves 4 on the outer surface of each link,the contact area between the outer surface of the conveyer chaincomposed of such links and the objects being located thereon is reduced,whereby the frictional resistance between the chain and the objects isreduced, resulting in the improvement of the slidability of the outersurface of the conveyer chain relative to the objects being locatedthereon. In addition, even if hard, small impurities adhere onto theouter surface of the conveyer chain, the objects being located thereonshall drop the impurities into the grooves 4 while they slip on theconveyer chain. Therefore, the bottom surfaces of the objects beingconveyed are not scratched by such impurities. In the present invention,the materials of the links are not specifically defined, provided thatthe kinetic friction coefficient of the outer surface of each linkitself may fall within the defined range. Therefore, any known materialsof, for example, metals, resins and ceramics can be used, but resins arepreferred. The kind of the resins for use in the present invention isalso not specifically defined. Employable are various thermoplasticresins and thermosetting resins, including, for example, polyacetalresins, polyether-imide resins, polyamidimide resins, polyimide resins,and liquid-crystalline polymers such as liquid-crystalline polyesters.

To these resins can be added, if desired, fluorine-containing resins,such as polytetrafluoroethylene, tetrafluoroethylene-hexafluoropropylenecopolymers, polytrichlorofluoroethylene, andtetrafluoroethylene-perfluoroalkyl vinyl ether copolymers, and alsolubricants, provided that such additives do not interfere with theobjects of the present invention.

As the materials of the links having small hills and grooves on theirouter surfaces, most preferred are compositions comprising polyamidimideresins and fluorine-containing resins, of which the fluorine-containingresin content is preferably from 0.3 to 40% by weight, more preferablyfrom 5 to 30% by weight.

The materials of the metal pins are not also specifically defined andmay include, for example, iron steel, stainless steel, resins, andceramics.

It is also preferred to apply a lubricant onto the outer surfaces of thelinks on which objects to be conveyed are located. Preferred examples ofthe lubricants are water and soapy water.

The lubricant as applied onto the outer surfaces of the links is kept inthe grooves formed thereon and is gradually released out onto the outersurfaces to cover them. Therefore, the slidability of the outer surfacesof the links can be improved more even when only a small amount of sucha lubricant is applied onto the outer surfaces.

Next, the chain of the invention in which the outer surfaces of thelinks, on which objects to be conveyed are located, are made from acomposition comprising a polyamidimide resin and a fluorine-containingresin is described in detail.

In this embodiment of the invention, the shape of each link is notspecifically defined, provided that a plurality of the links are linkedendlessly to one another in such a manner that the front end of one linkis movably linked to the back end of the adjacent link via a linking pinto form a type of conveyer chain.

Since polyamidimide resins have excellent abrasion resistance, the lifeof the chain made from such resins is longer than that of the othersmade from other resins such as polyether-imide resins orpolyoxymethylene resins. In general, the conveyer chain of the presentinvention is used while being hung over two or more sprockets underrelatively high tension. Since polyamidimide resins have excellent creepresistance, the conveyer chain composed of these is neither elongatednor loosened. Therefore, it is unnecessary to artificially control theconveyer chain to prevent it from being loosened, and the labor formaintaining the conveyer chain can be saved.

Any known polyamidimide resins can be used in the present invention,including commercially-available ones such as, for example, "TI Polymer"produced by Toray Industries, Inc.

The fluorine-containing resins for use in the present invention include,for example, polytetrafluoroethylene,tetrafluoroethylene-hexafluoropropylene copolymers,polytrichlorofluoroethylene, and tetrafluoroethylene-perfluoroalkylvinyl ether copolymers. Of these, preferred is polytetrafluoroethylene(PTFE). The amount of the fluorine-containing resin to be added ispreferably from 0.3 to 40% by weight, more preferably from 5 to 30% byweight, of the total weight of the composition. The polyamidimide resinfor use in the present invention may be combined with any otherthermoplastic resins, provided that the additional resins do notinterfere with the effects of the present invention.

The structure of the chain, of which at least a part of the outersurface is made from a resin composition comprising a polyamidimideresin and a fluorine-containing resin, can have not only a reducedkinetic friction coefficient at its outer surface but also even anoptimized critical PV value. Using the chain, therefore, it is possibleto smoothly slide objects on its surface even when no lubricant isapplied thereto.

The method of making links for the chain from the composition comprisinga polyamidimide resin and a fluorine-containing resin is notspecifically defined. For example, employable is a method of injectionmolding to directly produce links, and also a method of first shapingrough bodies through extrusion or compression molding followed bycutting and finishing the bodies into links with desired shapes.

In the present invention where at least the outer surfaces of the links,on which objects to be conveyed are located, are made from the resincomposition such as that mentioned above, the slidability of the outersurfaces of the links is improved. However, in order to prolong the lifeof the links, to save the labor for the maintenance of the links, tofacilitate the shaping of the links through injection molding, and tosimplify the structure of the links, it is desirable that the links areentirely made from the resin composition.

In addition, in order to further improve the physical properties, suchas heat resistance and strength, of the links of the chain, it isdesirable that the links are, after having been shaped, subjected toheat treatment. This is because shaped articles made from compositionscomprising polyamidimide resins and fluorine-containing resins may haveimproved hardness, strength and heat resistance, if they areheat-treated. Therefore, the life of the chain composed of suchheat-treated links may be much more prolonged. Where the links of thechain of the invention are produced through injection molding, they aregenerally heat-treated after having been shaped by injection molding. Ifthe links are produced through extrusion or compression molding, it isdesirable that the shaped bodies are heat-treated and thereafter cutinto the links. However, such is not limitative. It is also possibleeither to first cut the shaped bodies into the links and thereafterheat-treat the thus-cut links, or to carry out the heat treatment bothbefore and after the cutting step.

The heat treatment may be conducted at 200° C. or higher preferably at150° C. or higher. The time for the heat treatment may be 12 hours orlonger, preferably 24 hours or longer.

The combination of the formation of the plural small hills and grooveson the outer surfaces of the links and the use of the compositioncomprising a polyamidimide resin and a fluorine-containing resin as thematerial of the links can produce a conveyer chain having a much morereduced kinetic friction coefficient.

EXAMPLES Example 1

Links for a conveyer chain each having long, small hills with atrapezoidal cross-sectional profile and grooves with aninverted-trapezoidal cross-sectional profile on their outer surfaces, onwhich objects to be conveyed are put, were produced through injectionmolding of a polyamidimide resin, TI-5013 (produced by Toray Industries,Inc.). In these, the hills and the grooves were formed alternately at apitch of the hills of 1 mm and at a depth of the grooves of 1 mm.

A lubricant, soapy water was applied to the length, which were thensubjected to a friction test using a Suzuki-type Abrasion Tester. Inthis test, an aluminium object was slid on the outer surface of thelink, on which objects to be conveyed are located, at a pressure of 5kg/cm² and at a peripheral velocity of 20 m/min, for 1 hour. As a resultof this test, the kinetic friction coefficient of the outer surface ofthe tested link was found to be 0.19.

A plurality of these links were prepared. These were linked endlessly toone another, as in FIG. 1, to produce a conveyer chain. Soapy water wasapplied to this, and the conveyer chain which was used in a conveyersystem line where many 350 ml cans were conveyed on the chain, whereuponthe bottom surfaces of the cans being conveyed were visually observed asto whether or not they were scratched. In this test line, the percentageof the scratched cans was 8%.

Comparative Example 1

Links were produced in the same manner as in Example 1, except thattheir outer surfaces had neither hills nor grooves but were flat, andsubjected to the same friction test. The kinetic friction coefficient ofthe outer surface of the tested link was 0.34, which was larger thanthat in Example 1. Using the Suzuki-type Abrasion Tester, the criticalPV value of the link was measured, relative to the aluminium object, tobe 200.

A conveyer chain was made of these links, which was then used in thesame conveyer system line as in Example 1. In this test line, thepercentage of the scratched cans was 18%.

Example 2

Links were made of an oil-containing polyacetal resin sheet, on theouter surfaces of which were formed long, small hills having atrapezoidal cross-sectional profile and grooves having aninverted-trapezoidal cross-sectional profile, alternately at a pitch ofthe hills of 1 mm and at a depth of the grooves of 1 mm. A lubricant,soapy water was applied to these. These were subjected to the samefriction test as in Example 1 where an aluminium object was slid ontheir outer surfaces. As a result of this test, the kinetic frictioncoefficient of the outer surface of the tested link was 0.10.

A conveyer chain was made of these links, which was then used in thesame conveyer system line as in Example 1. In this test line, thepercentage of the scratched cans was 10%.

Example 3

Links each having the same shape as in Example 1 but having a flat outersurface were produced through injection molding of a composition of apolyamidimide resin, "TI Polymer" TI-5013 (produced by Toray Industries,Ltd.) containing 10% by weight of PTFE. These were subjected to the samefriction test as in Example 1 under the same condition. As a result ofthe test, the kinetic friction coefficient of the outer surface of thetested link was found to be 0.15.

Using the Suzuki-type Abrasion Tester, the critical PV value of the linkwas measured, relative to the aluminium object, to be 1500.

These links were heat-treated at 260° C. for 96 hours, and then linkedto one another via metal pins to obtain a conveyer chain. This conveyerchain was used in a conveyer system line, where cylindrical, 250 ml canswere conveyed on the chain with often sliding the cans relatively on theouter surface of the chain. In this, the chain running speed was 80m/min. In this test line, the line ran well continuously for 3 monthswithout applying any lubricant to the chain. No dust was formed due tothe friction between the cans being conveyed and the surface of thechain, and the slidability of the outer surface of the chain was keptgood. Even when the chain running speed was increased up to 120 m/min,the line still ran well continuously for 3 months.

Comparative Example 2

For comparison, a polyacetal resin was used and tested under the samecondition as above. As a result, the kinetic friction coefficient of theouter surface of the link tested was found to be 0.30.

These rinks were linked to one another via metal pins to obtain aconveyer chain. This was used in the same line as in Example 3 where thechain running speed was 80 m/min. In this test line, however, the cansbeing conveyed frequently fell down. Therefore, it is difficult to usethis conveyer chain in practical conveyer system lines.

Example 4

Links having the same shape and having the same hills and grooves ontheir outer surfaces as in Example 1 were produced through injectionmolding of a composition of a polyamidimide resin, "TI Polymer" TI-5013(produced by Toray Industries, Ltd.) containing 10% by weight of PTFE.These were subjected to the same test as in Example 1, in which thekinetic friction coefficient of the outer surface of the tested link wasfound to be 0.15.

Using the Suzuki-type Abrasion Tester, the critical PV value of the linkwas measured, relative to the aluminium object, to be 1500.

These links were heat-treated at 260° C. for 96 hours, and then linkedto one another via metal pins to obtain a conveyer chain. This conveyerchain was used in a conveyer system line, where cylindrical, 250 ml canswere conveyed on the chain with often sliding the cans relatively on theouter surface of the chain. In this test line, the chain running speedwas 80 m/min. No dust was formed due to the friction between the cansbeing conveyed and the surface of the chain, and the slidability of theouter surface of the chain was kept good. In this, the line ran wellcontinuously for 3 months without applying any lubricant to the chain.Even when the chain running speed was increased up to 120 m/min, theline still run well continuously for 3 months.

Industrial Applicability

As has been described hereinabove, the conveyer chain of the presentinvention is useful as the means of conveying aluminium cans, glassbottles, PET bottles and other objects in a conveyer system line wheresuch objects are continuously produced. In particular, the conveyerchain is especially useful in a conveyer system line where the objectsbeing conveyed are required to be intermittently stopped on the conveyerchain in the middle of the line. In addition, the conveyer chain of theinvention is especially useful in high-temperature atmospheres whereconveyer chains with high strength are required.

We claim:
 1. A conveyor chain comprising a plurality of links linkedendlessly to one another in such a manner that the front end of one linkis movably linked to the back end of the adjacent link via a linkingpin, wherein each link has an outer surface on which objects areconveyed, wherein the outer surface of each link has a plurality ofsmall hills each having a trapezoidal cross section, and a plurality ofgrooves having a complimentary inverted trapezoidal cross section formedthereon and wherein the outer surface has a kinetic friction coefficientof less than 0.3 as measured in a test where an aluminum object is slidagainst the outer surfaces of the links at a pressure of 5 kg/cm² and ata speed of the chain of 20 m/min and wherein each of said plurality oflinks consist essentially of polyamidimide resin and afluorine-containing resin wherein the fluorine content is from about 0.3to 40% by weight of the total weight of the composition.
 2. The conveyerchain as claimed in claim 1, wherein the links are produced throughinjection molding of a composition comprising a polyamidimide resin anda fluorine-containing resin followed by heat-treating the molded links.3. The conveyer chain as claimed in claim 1, wherein the plurality ofsmall hills and grooves are formed by alternately providing a pluralityof long, small hills and a plurality of grooves therebetween.
 4. Theconveyer chain as claimed in claim 3, wherein the plurality of long,small hills and the plurality of grooves therebetween are formedalternately and in parallel to one another in the moving direction ofthe links.
 5. The conveyor chain as claimed in claim 1, wherein theplurality of small hills and grooves are formed by providing a pluralityof long grooves that extend in the moving direction of the links andsaid outer surface is further provided with a plurality of long groovesthat extend in the transverse direction relative to the movingdirection, thus defining a number of independent small hills each beingsurrounded by these grooves.
 6. The conveyer chain as claimed in claim1, wherein the links are produced by shaping a composition comprising apolyamidimide resin and a fluorine-containing resin through extrusion orcompression molding, then heat-treating the shaped bodies, and cuttingthem into links.
 7. The conveyor chain of claim 1, wherein the pitch ofthe long, small hills is from 0.5 to 2.0 mm.
 8. The conveyor chain ofclaim 1, wherein the depth of the grooves is from 0.2 mm to 2.0 mm. 9.The conveyor chain as claimed in claim 1, wherein a lubricant is appliedonto the outer surfaces of the links.
 10. Use of the conveyer chain asclaimed in claim 1, wherein the objects being conveyed on the chain areslid on at least a part of the outer surface of the chain and relativelyto the outer surface thereof.